Effects of estrogen on the mechanical behavior of the human Achilles tendon in vivo

Predicting Dynamic Foot Function From Static Foot Posture: Comparison Between Visual Assessment, Motion Analysis, and a Commercially Available Depth Camera

STUDY DESIGN :Controlled laboratory study.

OBJECTIVE

To evaluate the ability of 3 methods to assess static foot posture to predict rearfoot and midfoot kinematics during gait.

BACKGROUND

Static foot posture is commonly used clinically to infer dynamic function. Limitations of static clinical assessments may be overcome through advances in technologies, including commercially available depth cameras.

METHODS

The Foot Posture Index (FPI) of 31 males (average age, 22.5 years) was assessed using visual observation, a 3-D motion-analysis system, and a depth camera. Pearson correlations were used to evaluate relationships between FPI items and rearfoot and midfoot kinematics during walking. The ability of the static variables to predict dynamic function was assessed using multiple linear regression.

RESULTS

Most FPI items (85%) were not correlated with foot kinematics, regardless of assessment method. There were 6 fair to moderate correlations between visual FPI items and total rearfoot (r = -0.36 to -0.39, P<.05) and midfoot (r = 0.37 to 0.61, P<.05) motion, 2 fair correlations between 3-D motion-analysis FPI items and total midfoot (r = -0.43, P = .02) and peak rearfoot (r = -0.40, P = .03) motion, and 2 fair correlations between the depth-camera FPI items and average rearfoot (r = -0.38 to 0.44, P<.05) motion. Visual assessment of the FPI provided the best prediction model, explaining 37% of the variance in total midfoot inversion/eversion.

CONCLUSION

Static measures of foot posture are weakly correlated with rearfoot or midfoot kinematics, and have limited dynamic prediction ability. Our findings suggest that the FPI may not be an accurate representation of rearfoot or midfoot movement during walking, regardless of the measurement technique employed.

Achilles tendons from decorin- and biglycan-null mouse models have inferior mechanical and structural properties predicted by an image-based empirical damage model

Achilles tendons are a common source of pain and injury, and their pathology may originate from aberrant structure function relationships. Small leucine rich proteoglycans (SLRPs) influence mechanical and structural properties in a tendon-specific manner. However, their roles in the Achilles tendon have not been defined. The objective of this study was to evaluate the mechanical and structural differences observed in mouse Achilles tendons lacking class I SLRPs; either decorin or biglycan. In addition, empirical modeling techniques based on mechanical and image-based measures were employed. Achilles tendons from decorin-null (Dcn(-/-)) and biglycan-null (Bgn(-/-)) C57BL/6 female mice (N=102) were used. Each tendon underwent a dynamic mechanical testing protocol including simultaneous polarized light image capture to evaluate both structural and mechanical properties of each Achilles tendon. An empirical damage model was adapted for application to genetic variation and for use with image based structural properties to predict tendon dynamic mechanical properties. We found that Achilles tendons lacking decorin and biglycan had inferior mechanical and structural properties that were age dependent; and that simple empirical models, based on previously described damage models, were predictive of Achilles tendon dynamic modulus in both decorin- and biglycan-null mice.

Jump-landing biomechanics and knee-laxity change across the menstrual cycle in women with anterior cruciate ligament reconstruction

CONTEXT

Of the individuals able to return to sport participation after an anterior cruciate ligament(ACL) injury, up to 25% will experience a second ACL injury. This population may be more sensitive to hormonal fluctuations, which may explain this high rate of second injury.

OBJECTIVE

To examine changes in 3-dimensional hip and knee kinematics and kinetics during a jump landing and to examine knee laxity across the menstrual cycle in women with histories of unilateral noncontact ACL injury.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 women (age = 19.6 ± 1.3 years, height = 168.6 ± 5.3 cm, mass = 66.2 ± 9.1 kg) with unilateral, noncontact ACL injuries.

INTERVENTION(S)

Participants completed a jump-landing task and knee-laxity assessment 3 to 5 days after the onset of menses and within 3 days of a positive ovulation test.

MAIN OUTCOME MEASURE(S)

Kinematics in the uninjured limb at initial contact with the ground during a jump landing, peak kinematics and kinetics during the loading phase of landing, anterior knee laxity via the KT-1000, peak vertical ground reaction force, and blood hormone concentrations (estradiol-β-17, progesterone, free testosterone).

RESULTS

At ovulation, estradiol-β-17 (t = -2.9, P = .009), progesterone (t = -3.4, P = .003), and anterior knee laxity (t = -2.3, P = .03) increased, and participants presented with greater knee-valgus moment (Z = -2.6, P = .01) and femoral internal rotation (t = -2.1, P = .047). However, during the menses test session, participants landed harder (greater peak vertical ground reaction force; t = 2.2, P = .04), with the tibia internally rotated at initial contact (t = 2.8, P = .01) and greater hip internal-rotation moment (Z = -2.4, P = .02). No other changes were observed across the menstrual cycle.

CONCLUSIONS

Knee and hip mechanics in both phases of the menstrual cycle represented a greater potential risk of ACL loading. Observed changes in landing mechanics may explain why the risk of second ACL injury is elevated in this population.

In vitro tenocyte metabolism in aging and oestrogen deficiency

Little is known about tendons and tenocyte biological behaviour during aging and, especially, oestrogen deficiency. The aim of this study was to evaluate in vitro the proliferation and metabolism of tenocytes isolated from the Achilles tendons of ovariectomised (OVX), middle-aged (OLD) and young (YOUNG) rats. An in vitro model of micro-wound healing was also used to assess age and oestrogen deficiency differences in tendon healing. In standard culture condition, OLD and OVX tenocytes showed a significantly lower proliferation rate, collagen I, aggrecan and elastin than YOUNG ones. In OVX group, fibronectin and elastin significantly decreased in comparison to YOUNG and OLD groups, respectively, whereas vascular endothelial growth factor and metalloproteinases-13 increased than those of both YOUNG and OLD groups. In the micro-wound healing model, tenocytes from both OVX and OLD showed a significantly lower healing rate, proliferation rate, collagen I and nitrix oxide in comparison to YOUNG. OVX elastin value was significantly lower than YOUNG one and OVX healing rate and cell migration speed, proliferation rate and fibronectin results were lower, whereas collagen III and metalloproteinase-13 higher in comparison to both YOUNG and OLD groups. These results highlighted how aging and, more significantly, oestrogen deficiency negatively affect tendon metabolism and healing. Our work improves the body of knowledge on the effects of senescence and oestrogen deficiency on tenocyte behaviour and allows further studies to find solution for the prevention of tendon injuries in aging and menopause.

Gender differences in fascicular lengthening during eccentric contractions: the role of the patella tendon stiffness

AIM

Elastic tendons have been suggested to attenuate fascicle lengthening during eccentric contractions; however, there is no in vivo evidence to support this hypothesis. Therefore, the aim of this study was to determine whether patella tendon stiffness modulates vastus lateralis (VL) fascicle lengthening during eccentric contractions in males and females.

METHOD

Vastus lateralis and patella tendon properties were measured in males and females owing to previously reported intrinsic gender differences in tendon properties. During maximal voluntary eccentric knee extensions, VL fascicle lengthening and torque were recorded at every 10° (range of motion 20-90°).

RESULTS

A significant correlation between maximal patella tendon stiffness and change in fascicle length (r=0.476, P=0.023) was observed. Similarly, there was a significant correlation between maximal Young's modulus and change in fascicle length (r=0.470, P=0.049). As expected, patella tendon stiffness and Young's modulus were significantly higher in males compared with females (P<0.05). Interestingly, change in VL fascicle length during the eccentric contractions was significantly greater in males compared with females (P<0.05). Based on patella tendon moment arm measurements, VL muscle-tendon unit elongation was estimated to be significantly greater in males compared with females (5.24 and 4.84 cm respectively).

CONCLUSION

The significant difference in fascicle lengthening during eccentric contractions may be partly explained by the significantly higher patella tendon moment arm, patella tendon stiffness and Young's modulus found in males compared with females. The current study provides in vivo evidence to support the hypothesis that the tendon acts as a 'mechanical buffer' during eccentric contractions.

Menopause, estrogens and frailty

The controversy surrounding the results from the Women's Health Initiative (WHI) trials published a decade ago caused a significant decline in the use of menopausal hormone replacement therapy. However, these results have been vehemently contested and several lines of evidence suggest that in perimenopausal and non-obese women, estrogen therapy may indeed be of benefit. There is ample proof that menopause causes a loss of musculoskeletal tissue mass and quality, thereby causing a loss of health and quality of life. There is also solid evidence that hormone replacement therapy in itself prevents most of these effects in connective tissue in itself. Besides the independent, direct effects on the musculoskeletal tissues, estrogen deficiency also reduces the ability to adequately respond and adapt to external mechanical and metabolic stressors, e.g. exercise, which are otherwise the main stimuli that should maintain musculoskeletal integrity and metabolic function. Thus, normophysiological estrogen levels appear to exert a permissive effect on musculoskeletal adaptations to loading, thereby likely improving the outcome of rehabilitation following critical illness, musculoskeletal trauma or orthopedic surgical therapy. These effects add to the evidence supporting the use of estrogen therapy, particularly accelerated gain of functional capacity and independence following musculoskeletal disuse.

Reliability and validity of the Microsoft Kinect for evaluating static foot posture

BACKGROUND

The evaluation of foot posture in a clinical setting is useful to screen for potential injury, however disagreement remains as to which method has the greatest clinical utility. An inexpensive and widely available imaging system, the Microsoft Kinect™, may possess the characteristics to objectively evaluate static foot posture in a clinical setting with high accuracy. The aim of this study was to assess the intra-rater reliability and validity of this system for assessing static foot posture.

METHODS

Three measures were used to assess static foot posture; traditional visual observation using the Foot Posture Index (FPI), a 3D motion analysis (3DMA) system and software designed to collect and analyse image and depth data from the Kinect. Spearman's rho was used to assess intra-rater reliability and concurrent validity of the Kinect to evaluate foot posture, and a linear regression was used to examine the ability of the Kinect to predict total visual FPI score.

RESULTS

The Kinect demonstrated moderate to good intra-rater reliability for four FPI items of foot posture (ρ = 0.62 to 0.78) and moderate to good correlations with the 3DMA system for four items of foot posture (ρ = 0.51 to 0.85). In contrast, intra-rater reliability of visual FPI items was poor to moderate (ρ = 0.17 to 0.63), and correlations with the Kinect and 3DMA systems were poor (absolute ρ = 0.01 to 0.44). Kinect FPI items with moderate to good reliability predicted 61% of the variance in total visual FPI score.

CONCLUSIONS

The majority of the foot posture items derived using the Kinect were more reliable than the traditional visual assessment of FPI, and were valid when compared to a 3DMA system. Individual foot posture items recorded using the Kinect were also shown to predict a moderate degree of variance in the total visual FPI score. Combined, these results support the future potential of the Kinect to accurately evaluate static foot posture in a clinical setting.

Impact of oral contraceptive use and menstrual phases on patellar tendon morphology, biochemical composition, and biomechanical properties in female athletes

Sex differences exist with regards to ligament and tendon injuries. Lower collagen synthesis has been observed in exercising women vs. men, and in users of oral contraceptives (OC) vs. nonusers, but it is unknown if OC will influence tendon biomechanics of women undergoing regular training. Thirty female athletes (handball players, 18-30 yr) were recruited: 15 long-term users of OC (7.0 ± 0.6 yr) and 15 nonusers (>5 yr). Synchronized values of patellar tendon elongation (obtained by ultrasonography) and tendon force were sampled during ramped isometric knee extensor maximum voluntary contraction to estimate mechanical tendon properties. Furthermore, tendon cross-sectional area and length were measured from MRI images, and tendon biopsies were obtained for analysis of tendon fibril characteristics and collagen cross-linking. Overall, no difference in tendon biomechanical properties, tendon fibril characteristics, or collagen cross-linking was observed between the OC users and nonusers, or between the different phases of the menstrual cycle. In athletes, tendon cross-sectional area in the preferred jumping leg tended to be larger than that in the contralateral leg (P = 0.09), and a greater absolute (P = 0.01) and normalized tendon stiffness (P = 0.02), as well as a lower strain (P = 0.04), were observed in the jumping leg compared with the contralateral leg. The results indicate that long-term OC use or menstrual phases does not influence structure or mechanical properties of the patellar tendon in female team handball athletes.

Achilles tendon rupture in women

BACKGROUND

The incidence of Achilles rupture appears to be less in women, although this notion has not been specifically investigated in the literature.

METHODS

The medical records of 7 foot-and-ankle orthopaedic surgeons at 1 institution were reviewed by Current Procedural Terminology (code 27650) and International Classification of Diseases-9 (code 727.67) to establish all Achilles tendon ruptures seen and/or treated by these surgeons. Sex, age, side, and mechanism of injury were recorded. Whether the patient had an acute Achilles tendon rupture or nonacute Achilles pathology was also noted.

RESULTS

A total of 468 patients were identified, of whom 358 had acute ruptures: 302 male and 56 female (5.39:1). Patients with acute ruptures were significantly younger than those with nonacute pathology (43.8 vs 55.1, P < .001). For acute ruptures, the mean age was not significantly different between men and women (43.9 vs 43.2; P = .780). Athletic activity was causative in 243 of 302 men (80.5%) and in 40 of 56 women (71.4%). This difference was not statistically significant (P = .130). Six men (2.0%) and 6 women (10.7%) had comorbidities that were thought to increase their risk of rupture (P = .005).

CONCLUSION

Achilles tendon rupture is more common in men than women. Previous studies using the aforementioned codes to identify patients without chart review may have overestimated the number of women with acute Achilles tendon rupture.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Triceps surae activation is altered in male runners with Achilles tendinopathy

Achilles tendinopathy is a common injury in running sports however the exact etiology of Achilles injury is still unclear. In recent years, altered neuromotor recruitment patterns of the triceps surae have been hypothesized to create differential intra-tendinous loads leading to pathology; however, this hypothesis has not been investigated. Further, the effect foot orthoses may have on neuromotor recruitment of the triceps surae in Achilles tendinopathy has not been investigated.

METHODS

The electromyographic activity of the triceps surae was recorded during an over-ground running task. Fifteen Achilles injured participants and 19 asymptomatic controls were assessed in a footwear only condition. The Achilles injured participants were also assessed running in a pre-fabricated foot orthoses.

RESULTS

In Achilles injured participants, there was a significant difference between soleus and lateral gastrocnemius offset times during running compared to the asymptomatic controls (p<0.05). There were no significant differences in triceps surae muscle activity between the footwear only and footwear and orthoses condition in the Achilles injured participants.

CONCLUSIONS

The finding that triceps surae activity is altered in participants with Achilles tendinopathy may have clinical importance as it suggests that intra-tendinous loads are altered which may contribute to pathological changes. Further, foot orthoses have no immediate effect on the neuromotor control of the triceps surae.

Biomechanical approaches to identify and quantify injury mechanisms and risk factors in women's artistic gymnastics

Targeted injury prevention strategies, based on biomechanical analyses, have the potential to help reduce the incidence and severity of gymnastics injuries. This review outlines the potential benefits of biomechanics research to contribute to injury prevention strategies for women's artistic gymnastics by identification of mechanisms of injury and quantification of the effects of injury risk factors. One hundred and twenty-three articles were retained for review after searching electronic databases using key words, including 'gymnastic', 'biomech*', and 'inj*', and delimiting by language and relevance to the paper aim. Impact load can be measured biomechanically by the use of instrumented equipment (e.g. beatboard), instrumentation on the gymnast (accelerometers), or by landings on force plates. We need further information on injury mechanisms and risk factors in gymnastics and practical methods of monitoring training loads. We have not yet shown, beyond a theoretical approach, how biomechanical analysis of gymnastics can help reduce injury risk through injury prevention interventions. Given the high magnitude of impact load, both acute and accumulative, coaches should monitor impact loads per training session, taking into consideration training quality and quantity such as the control of rotation and the height from which the landings are executed.

The effects of oral contraceptive use on muscle stiffness across the menstrual cycle

OBJECTIVE

To determine the effect of oral contraceptives (OC) on hamstring neuromechanics and lower extremity stiffness across the menstrual cycle (MC).

DESIGN

Causal comparative.

SETTING

Research laboratory.

PARTICIPANTS

Thirty, healthy, normally menstruating female volunteers who were using OC (OC group, n = 15) or not (non-OC group, n = 15).

ASSESSMENT OF RISK FACTORS

Stiffness and hamstring neuromechanics were assessed at 2 points of the MC corresponding to low (menses) and high (ovulation) hormone concentrations. Menses testing took place 3 to 5 days after the onset of menses (or pills 3-5 for the OC group). Ovulation test session occurred 2 to 4 days after ovulation identified using a commercial ovulation kit (or pills 15-17 in the OC group).

MAIN OUTCOME MEASURES

Lower extremity stiffness and hamstring neuromechanics [stiffness, electromechanical delay, rate of force production (RFP), time to 50% peak force (T50%)] and blood plasma concentrations of estradiol-β-17, free testosterone, and progesterone.

RESULTS

Estradiol-β-17, free testosterone, and progesterone increased at ovulation in the non-OC group and remained constant in the OC group. No changes were observed across the MC or between the groups in other variables (P > 0.05).

CONCLUSIONS

Although previous literature suggests a prophylactic effect of OC use with respect to musculoskeletal injury risk, our results indicate that OC use does not affect muscle properties in manners thought to reduce ACL injury risk.

Mechanical properties of the human Achilles tendon, in vivo

BACKGROUND

Ultrasonography has been widely applied for in vivo measurements of tendon mechanical properties. Assessments of human Achilles tendon mechanical properties have received great interest. Achilles tendon injuries predominantly occur in the tendon region between the Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction i.e. in the free Achilles tendon. However, there has been no adequate ultrasound based method for quantifying the mechanical properties of the free human Achilles tendon. This study aimed to: 1) examine the mechanical properties of the free human Achilles tendon in vivo by the use of ultrasonography and 2) assess the between-day reproducibility of these measurements.

METHODS

Ten male subjects had the Achilles tendon moment arm length, Achilles tendon cross sectional area and free Achilles tendon length determined. All subjects performed isometric plantarflexion ramp contractions to assess between-day reproducibility on two separate days. Simultaneous ultrasonography based measurements of Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction displacement together with Achilles tendon force estimates yielded free Achilles tendon mechanical properties.

FINDINGS

Free Achilles tendon maximal force, deformation and stiffness were 1924 (SD 229) N, 2.2 (SD 0.6) mm and 2622 (SD 534) N/mm on day 1. For between-day reproducibility there were no significant differences between days for free Achilles tendon mechanical properties. The between-day correlation coefficient and typical error percent were 0.81 and 5.3% for maximal Achilles tendon force, 0.85 and 11.8% for maximal Achilles tendon deformation and 0.84 and 8.8% for Achilles tendon stiffness respectively. Last, osteotendinous junction proximal displacement on average contributed with 71 (SD 12) % of proximal myotendinous junction displacement.

INTERPRETATION

This study, for the first time, presents an ultrasonography based in vivo method for measurement of free AT mechanical properties. The method is applicable for evaluation of free human Achilles tendon mechanical properties in relation to training, injury and rehabilitation.

Lower limb biomechanics during running in individuals with achilles tendinopathy: a systematic review

Background

Abnormal lower limb biomechanics is speculated to be a risk factor for Achilles tendinopathy. This study systematically reviewed the existing literature to identify, critique and summarise lower limb biomechanical factors associated with Achilles tendinopathy.

Methods

We searched electronic bibliographic databases (Medline, EMBASE, Current contents, CINAHL and SPORTDiscus) in November 2010. All prospective cohort and case-control studies that evaluated biomechanical factors (temporospatial parameters, lower limb kinematics, dynamic plantar pressures, kinetics [ground reaction forces and joint moments] and muscle activity) associated with mid-portion Achilles tendinopathy were included. Quality of included studies was evaluated using the Quality Index. The magnitude of differences (effect sizes) between cases and controls was calculated using Cohen's d (with 95% CIs).

Results

Nine studies were identified; two were prospective and the remaining seven case-control study designs. The quality of 9 identified studies was varied, with Quality Index scores ranging from 4 to 15 out of 17. All studies analysed running biomechanics. Cases displayed increased eversion range of motion of the rearfoot (d = 0.92 and 0.67 in two studies), reduced maximum lower leg abduction (d = -1.16), reduced ankle joint dorsiflexion velocity (d = -0.62) and reduced knee flexion during gait (d = -0.90). Cases also demonstrated a number of differences in dynamic plantar pressures (primarily the distribution of the centre of force), ground reaction forces (large effects for timing variables) and also showed reduced peak tibial external rotation moment (d = -1.29). Cases also displayed differences in the timing and amplitude of a number of lower limb muscles but many differences were equivocal.

Conclusions

There are differences in lower limb biomechanics between those with and without Achilles tendinopathy that may have implications for the prevention and management of the condition. However, the findings need to be interpreted with caution due to the limited quality of a number of the included studies. Future well-designed prospective studies are required to confirm these findings.

Effects of ovariectomy and resistance training on MMP-2 activity in rat calcaneal tendon

Tendon remodeling relies on extracellular matrix (ECM) restructuring by the matrix metallopeptidases (MMPs). The aim of this study was to investigate MMP-2 activity in different regions of the calcaneal tendon (CT) after resistance training (RT) in ovariectomized rats. Wistar adult female rats were grouped into sedentary (Sed-Intact), ovariectomized sedentary (Sed-Ovx), acute exercise (AcuteEx-Intact), ovariectomized acute exercise (AcuteEx-Ovx), resistance trained (ChronicEx-Intact), and ovariectomized resistance trained (ChronicEx-Ovx) (n = 10 each group). The RT protocol required the animals to climb a 1.1-m vertical ladder with weights attached to their tail. The sessions were performed once every 3 days with 4-9 climbs and 8-12 dynamic movements per scaling. The acute groups performed one session and the chronic groups underwent 12 weeks of RT. There was an increase in total MMP-2 activity in Sed-Ovx, AcuteEx-Intact, and ChronicEx-Intact compared with that in Sed-Intact in the proximal region of CT. AcuteEx-Ovx exhibited higher total MMP-2 than Sed-Ovx and AcuteEx-Intact in the distal region of CT. Chronic-Ovx presented lower total MMP-2 activity than Sed-Ovx and Chronic-Intact in the distal region of tendon. The active MMP-2 was higher for the AcuteEx-Ovx than Sed-Ovx and AcuteEx-Intact in proximal region of tendon. There was higher active MMP-2 in the distal region of tendon in the Acute-Ovx than in the Sed-Ovx and AcuteEx-Intact. Ovariectomy and resistance exercise modulate MMP-2 activity according to specific tendon region, indicating a differentiated tissue remodeling.

Estrogen receptor expression in posterior tibial tendon dysfunction: a pilot study

BACKGROUND

The pathophysiology of posterior tibial tendon dysfunction (PTTD) is poorly understood. It has been theorized that changes in hormone physiology may be a factor influencing tendon health. Estrogen's influence on the fibroblast has been studied in other musculoskeletal tissues. Gender differences in anterior cruciate ligament (ACL) injuries have been studied and it has been discovered that the Estrogen receptor (ER) as well as Progesterone receptor (PR) are expressed in the ACL.

MATERIAL AND METHODS

Eight patients with PTTD requiring surgery were enrolled in our pilot study. The mean patient age was 52.4 (range, 18 to 73) years. There were five female and three male patients. Tendon samples were harvested from diseased PTT. Tendon samples harvested from healthy PTT and healthy flexor digitorum longus (FDL) tendon were used as controls. Tendon samples were processed using specific protocols for total RNA isolation from hypocellular, dense connective tissues. ERα and ERβ transcripts were quantified using real time RT-PCR. Quantitative values were obtained from the threshold cycle (Ct) number at which the increase in fluorescent signal associated with an exponential increase of PCR products can be detected.

RESULTS

Transcripts of both ERα and ERβ were reproducibly detected in RNA samples isolated from our tendon samples. There was no difference in receptor expression between diseased and control tendon samples. There was no difference in receptor expression between male and female patients.

CONCLUSION

We found that the tenocyte of the PTT and FDL tendons express ERα and ERβ. Normal and diseased tendons of both male and female patients expressed both estrogen receptors.

CLINICAL RELEVANCE

Identifying ERα and ERβ gene expression in the fibroblast was an initial step in discovering whether tenocytes are targets for estrogen function. Estrogen receptors were identified indirectly by measuring receptor gene expression but we were unable to show a significant difference between diseased and control tendons.

Mechanical properties of the achilles tendon aponeurosis are altered in athletes with achilles tendinopathy

BACKGROUND

Achilles tendinopathy is a considerable problem for active people. The degenerative processes associated with tendinopathy may be associated with changes in the inherent mechanical properties of the musculotendinous unit.

PURPOSE

The purpose of this study was to compare Achilles tendon-aponeurosis strain between male athletes with and without Achilles tendinopathy.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Fifteen healthy men (age, 35 +/- 9 years; height, 1.78 +/- 0.05 m; mass, 79 +/- 11 kg) and 14 men with midportion Achilles tendinopathy (age, 40 +/- 8 years; height, 1.77 +/- 0.06 m; mass, 80 +/- 9 kg) who were all running over 20 km per week participated in the study. Each participant was tested in a single session that involved maximal isometric plantar flexion efforts being performed on a calf-raise apparatus while synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Achilles tendon-aponeurosis strain (%) was calculated by dividing tendon displacement during plantar flexion by resting tendon length (intrarater reliability: intraclass correlation coefficient = .92).

RESULTS

Participants in the Achilles tendinopathy group (5.2% +/- 2.6%) had significantly (P = .039) higher Achilles tendon-aponeurosis strain compared with the control group (3.4% +/- 1.8%). In contrast, there were no significant between-group differences for maximal isometric plantar flexion force.

CONCLUSION

Achilles tendon-aponeurosis strain is higher in male athletes with tendinopathy than those without. The results of this study provide a rationale for current clinical approaches to management of Achilles tendinopathy, whereby repetitive mechanical loading may impart a positive benefit through reduced compliance of the musculotendinous unit.

Hamstring antagonist torque generated in vivo following ACL rupture and ACL reconstruction

Hamstring motor behaviour and resultant antagonist torque during knee extension has been quantified in uninjured individuals however, the effect of ACL rupture and ACL reconstruction (ACLR) on the morphology of hamstring antagonist torque generated in vivo is unknown. The purpose of this cross-sectional study was to quantify the hamstring antagonist torque generated in vivo during isokinetic knee extension in ACLD and ACLR patients relative to uninjured control subjects. Ten male ACL deficient (ACLD) subjects (18-35 years), 14 matched males who had undergone ACLR using the bone-patellar tendon-bone graft and 22 matched male control subjects participated. We used a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10 degrees intervals from 80 degrees to 10 degrees knee flexion. Control group hamstring antagonist torque was significantly lower at 80-70 degrees knee flexion compared with that of the ACLD (% Diff=40.2; p=0.019) and ACLR (% Diff=34.8; p=0.036) groups. For all subject groups, hamstring antagonist torque demonstrated a descending-ascending curve; decreasing significantly from 80-70 degrees to 50-40 degrees knee flexion (% Diff=40.8 to 63.3; p=<0.001 to 0.009) but then increasing significantly from 50-40 degrees to 20-10 degrees knee flexion (% Diff=37.6 to 59.0; p=<0.001 to 0.012). ACL status and therefore, the ACL-hamstring reflex has little effect on the magnitude of hamstring antagonist torque generated during quadriceps-induced knee joint loading. Capsular afferents are thought to dictate the hamstring torque profile which decreased then increased during knee extension to maintain dynamic joint stability.

Tibial acceleration variability during consecutive gait cycles is influenced by the menstrual cycle

BACKGROUND

The relationship between the phases of the menstrual cycle and injury risk remains unclear. Neuromuscular function may be compromised during menstruation, which could result in reduced cyclicality of movement patterns. We hypothesize that mediolateral (varus/valgus) knee acceleration during running gait will possess increased variability during menstruation when compared to approximately ovulation in women who do not take the monophasic oral contraceptive pill (MOCP).

METHODS

Thirty-six women (18 MOCP users: MOCP group and 18 non-pill users: NP group) performed six-minute treadmill running trials at 10 km h(-1) with an accelerometer fixed to the proximal tibia. Trials were performed at menstruation and approximately equal ovulation (for the MOCP group at a similar stage of the cycle) in a randomized order. The cyclicality of gross mediolateral tibial acceleration during 15 consecutive strides was assessed using combined wavelet and autocorrelation analysis. Longitudinal and anteroposterior accelerations were also examined. Repeated measures analysis of variance (ANOVA) tests were performed to assess differences at each stage of the menstrual cycle (alpha=0.05).

FINDINGS

Gross mediolateral acceleration in the NP group had significantly (P=0.022) increased variability at the time of menstruation compared to approximately equal ovulation, and was also significantly (P=0.011) more variable than the MOCP group at the corresponding time point. No significant difference was observed for any measure in the MOCP group.

INTERPRETATION

Increased variability in the NP users at menstruation may be a result of compromised motor control strategies. This provides further evidence of variability in performance and motor control during menstruation, and may have implications for a female athlete's risk of injury.

Iliotibial band syndrome: an examination of the evidence behind a number of treatment options

Iliotibial band (ITB) syndrome (ITBS) is a common cause of distal lateral thigh pain in athletes. Treatment often focuses on stretching the ITB and treating local inflammation at the lateral femoral condyle (LFC). We examine the area's anatomical and biomechanical properties. Anatomical studies of the ITB of 20 embalmed cadavers. The strain generated in the ITB by three typical stretching maneuvers (Ober test; Hip flexion, adduction and external rotation, with added knee flexion and straight leg raise to 30 degrees ) was measured in five unembalmed cadavers using strain gauges. Displacement of the Tensae Fasciae Latae (TFL)/ITB junction was measured on 20 subjects during isometric hip abduction. The ITB was uniformly a lateral thickening of the circumferential fascia lata, firmly attached along the linea aspera (femur) from greater trochanter up to and including the LFC. The microstrain values [median (IQR)] for the OBER [15.4(5.1-23.3)me], HIP [21.1(15.6-44.6)me] and SLR [9.4(5.1-10.7)me] showed marked disparity in the optimal inter-limb stretching protocol. HIP stretch invoked significantly (Z=2.10, P=0.036) greater strain than the SLR. TFL/ITB junction displacement was 2.0+/-1.6 mm and mean ITB lengthening was <0.5% (effect size=0.04). Our results challenge the reasoning behind a number of accepted means of treating ITBS. Future research must focus on stretching and lengthening the muscular component of the ITB/TFL complex.

Menstrual cycle variations in oestradiol and progesterone have no impact on in vivo medial gastrocnemius tendon mechanical properties

BACKGROUND

Tendon tissue contains oestrogen receptors and is therefore likely to be responsive to female sex hormones. Here we examine any effect of levels of female sex hormones associated with the menstrual cycle phase on corresponding tendon mechanical properties.

METHODS

Fifteen healthy females aged 23 (SEM 1.0 years) underwent three assessments of medial gastrocnemius tendon mechanical properties. Assessments were carried out once during days 1-4, 12-14 and 20-23 (with day 1 being the first day of menstruation). Venous blood samples were taken on the same days as tendon properties assessments to quantify serum levels of oestradiol and progesterone.

FINDINGS

There was no significant difference in the stiffness of the medial gastrocnemius tendon over the course of the menstrual cycle (days 1-4, 65.08 (SEM 5.16 Nm m(-1)), days 12-14, 62.73 (SEM 5.82 Nm m(-1)), days 20-23, 66.74 (SEM 7.14 Nm m(-1))). There were also no significant differences in tendon length and cross-sectional area which led to no significant differences in Young's modulus values. No correlations were found between serum levels of oestradiol and/or progesterone and tendon stiffness and/or Young's modulus.

INTERPRETATION

Acute fluctuations in female sex hormones have no significant effect on medial gastrocnemius tendon mechanical properties. In a context where studies are often limited to selecting only oral contraceptive-users as participants in order to minimise potential noise related to the anticipated effects of menstrual cycle hormones on physical performance, our findings provide the basis for enabling the pooling of female tendon data, regardless of the phase of the menstrual cycle of individual participant.

Biomechanical and histological comparison of the influence of oestrogen deficient state on tendon healing potential in rats

Thirty-six female Sprague-Dawley rats were divided into two groups: oophrectomised (oestrogen deficient) rats and sham operated (oestrogen maintained) rats. Rats were sacrificed at six, ten, and 14 weeks. The rats were randomly chosen to have biomechanical evaluation on one side and histological evaluation on the other. Biomechanical testing was performed on an Instron machine to measure peak load. Histological sections were evaluated for cell proliferation, collagen-fibre organisation, fibroblast density, angiogenesis, inflammatory cells, chondroid and osseous metaplasia. Compared with the sham operated group, the oophrectomised group showed a lesser average maximum stress (42.9 N/m(2) versus 33.7 N/m(2)) at six weeks, which was significant (p < .05). Succeeding weeks showed no significant biomechanical differences between the two groups. The sham operated group showed greater inflammatory response, which was statistically significant (p < 0.05), and also revealed greater cell proliferation and density. The results of this study revealed that endogenous oestrogen may improve healing of the Achilles tendon in rats.

Combination of hormone replacement therapy and high physical activity is associated with differences in Achilles tendon size in monozygotic female twin pairs

Estrogen concentration has been suggested to play a role in tendon abnormalities and injury. In physically active postmenopausal women, hormone replacement therapy (HRT) has been suggested to decrease tendon diameter. We hypothesized that HRT use and physical activity are associated with Achilles tendon size and tissue structure. The study applied cotwin analysis of fourteen 54- to 62-yr-old identical female twin pairs with current discordance for HRT use for an average of 7 yr. Achilles tendon thickness and cross-sectional areas were determined by ultrasonography, and tendon structural organization was analyzed from the images using linear discriminant analysis (LDA). Maximal voluntary and twitch torques from plantar flexor muscles were measured. Serum levels of estradiol, estrone, testosterone, and sex hormone binding globulin were analyzed. Total daily metabolic equivalent score (MET-h/day) was calculated from physical activity questionnaires. Results showed that, in five physically active (MET > 4) pairs, the cotwins receiving HRT had greater estradiol level ( P = 0.043) and smaller tendon cross-sectional area than their sisters (63 vs. 71 mm2, P = 0.043). Among all pairs, Achilles tendon thickness and cross-sectional area did not significantly differ between HRT using and nonusing twin sisters. Intrapair correlation for Achilles tendon thickness was high, despite HRT use discordance ( r = 0.84, P < 0.001). LDA distinguished different tendon structure only from two of six examined twin pairs who had a similar level of physical activity. In conclusion, the effect of HRT on Achilles tendon characteristics independent of genetic confounding may be present only in the presence of sufficient physical activity. In physically active twin pairs, the higher level of estrogen seems to be associated with smaller tendon size.